The proposed area of research is response of monkey limbic neurons to visually-presented stimuli consisting of facial expressions of emotion in conspecifics. Behavioral experiments have shown that monkeys are capable of detection and responding differentially to pictures of apprehensive and calm monkey faces. Recent neurophysiologic studies have demonstrated the existence of face-responsive neurons in the amygdala and superior temporal sulcus. It is proposed to test neurons in the medial amygdala of Macaca radiata for responses to facial expression using color slides and videotapes of monkey faces. The distribution of face-responsive, and facial expression-responsive, neurons in other limbic regions will be explored with the goal of discovering the degree to which such a system is distributed throughout the brain. Secondly, the question as to whether face-responsiveness is simply an aspect of certain units' more general responsiveness to social signals in a variety of modalities, will be addressed experimentally. Finally, it is planned to begin comparing the properties of unit populations in isolation-reared monkeys to those in socially-reared monkeys, with the goal of describing the neural basis for disturbances in adult social behavior seen in isolation-reared monkeys. This research is of importance to clinical psychiatry since it studies the neural basis of empathy, essential to the clinician's grasp of the affective state of the patient. It may also provide insight into clinical disorders which have as one of their features a failure to interpret the affects of others appropriately.